To fit to the anatomies and individual characteristics of a user, hearing instruments are adapted by a standard procedure, for example as follows. In a first step, the hearing instrument is calibrated against a coupler. Also, an ear canal impression is taken in order to manufacture an ear mold. After the ear mold and the hearing instrument are manufactured, they are combined, and the Real-Ear-to-Coupler Difference (RECD) that, among others, accounts for the parameters ‘ear canal residual volume’ and ‘ear drum impedance’ is either estimated or measured.
Usually when the ear mold is available, the RECD is estimated with rather high error, leading to a bad initial fit. Alternatively, the RECD is measured in-situ. However, this in-situ RECD measurement is time-consuming and uncomfortable for the user as well as for the fitter, and the measurement accuracy is normally unknown.
U.S. Pat. No. 4,412,096 proposes to make an impression of a fast-curing material and to insert (press) a hearing aid receiver adapter into the impression. The resulting combination is then used for fitting and evaluating hearing aids. Especially, electroacoustic frequency response curves are measured. To this end (although not explicitly mentioned in U.S. Pat. No. 4,412,096), a probe tube microphone is required. The dimensions of the fast curing impression are changed upon insertion of the hearing aid receiver adapter, so that a tighter fit in the ear is achieved. This is perceived as an advantage according to U.S. Pat. No. 4,412,096, especially for reducing the possibility of acoustic feedback in fittings for patients with severe hearing loss. However, the method taught in U.S. Pat. No. 4,412,096 does not solve the problem of inaccuracies due to differences between the test set-up and the later use of the real hearing instrument.
It has already been proposed in PCT/CH2011/000277 to estimate the RECD by an impedance measurement using an ear canal microphone of an inserted hearing instrument.
It is an object of the present invention to provide a method of fitting a hearing instrument to a patient's (user's) ear, which method overcomes drawbacks of prior art methods, and which method especially reduces fitting efforts, is comfortable for the patient as well as the fitter and improves the first fit acceptance.